This invention relates to a circuit for generating scroll window signal in digital image apparatus, and particularly to a circuit for generating a scroll window signal capable of displaying two different screen sources, one on the right and the other on the left section of a common screen, simultaneously.
The prior techniques of displaying more than two screen sources simultaneously on a common screen such as a picture-in-picture system and a scroll screen displaying system are disclosed. The picture-in-picture system, which inserts a small screen into a main screen having a different screen source, has an advantage in that it can display an entire original source screen. However, it has a shortcoming in that it is difficult for the viewer to watch the full screen at a far distance because it is displayed with a small screen.
The method of displaying a small screen is a technique that displays two screens having different screen sources simultaneously on a common screen, one on the top and the other on the bottom, or one on the right and the other on the left, respectively. The system displays either the two pictures within the same size or one of them with large size covering the other small picture In the scroll window displaying system, although the entire part of the screen can be watched just as it is with its given size of a screen frame, the portion covered by scrolling cannot be displayed.
When a multiple screen is selected and displayed in a conventional scroll window displaying system, the desired portion of the screen is displayed by setting a window by means of handling selection keys of a top and bottom or a right and left. However, the top and bottom or the right and left window scrolling method has different screen selecting window pulses according to the types of a scroll screen. Then, each screen scroll type is selected by decoded window signal.
Therefore, it has a disadvantage in that the selecting logic circuit for selecting screen scroll types becomes complicated and the capacity for logic signal processing must be enlarged in scope.